CYC Motor Photon: One Electric Motor for Multiple Bikes

CYC Motor Photon is an electric motor that, thanks to its well-thought-out design, can be mounted on various bikes. This is one of the many advantages of electric drive systems, allowing traditional bikes to be converted into electric bikes. In this article, we discuss how to match the drive system to different bottom brackets.

Unexpected advantage of CYC Motor electric motors

It’s rarely mentioned—or not at all—but it’s one of the most significant advantages of all CYC Motor engines: the ability to mount them on almost any bicycle. In the case of the CYC Motor Photon model, the ease of transferring the motor between different bikes is the greatest. We’ll demonstrate this with a real-world example: we use the same motor in a “summer” full-suspension MTB and a “winter” rigid fatbike. We’ve also installed it in a gravel bike.

Matching the electric motor (kit) to a bike’s bottom bracket

For mid-drive motors used to convert bicycles, the most crucial compatibility factor is the bottom bracket, since the motor is installed directly into the BB shell. The CYC Motor Photon has been designed to fit practically any bottom bracket. Depending on the type, different mounting parts are required, but they are limited to a few inexpensive components:

• ISIS axle
• left BB mounting piece
• A-frame bracket (for fatbikes only)
• spacers
• BB92 adapter (for press-fit BBs only)

Secrets of mounting the electric motor to a bike

The Photon’s main motor module has an integrated sleeve that slides from the drive side (right) into the bottom bracket, then tightens from the left using a matching left-side part. Both sleeves are threaded and connect inside the BB shell. Tightening them firmly keeps the motor securely in place. This setup means the BB shell doesn’t even need internal threads—making it compatible with press-fit systems. Therefore, the only compatibility factors are the BB shell width and diameter. For press-fit BB92 brackets, which have a larger diameter than threaded BSA brackets, a special adapter is used to reduce the size. BB shell width is adjusted in another way.

As you may know, BB shells come in various widths—68 mm, 72 mm, 83 mm (most common), 92 mm (press-fit), and 100 mm and 120 mm (fatbikes). CYC Motor handles this by offering different ISIS axle lengths and left mounting pieces, along with combinations of spacers to adjust for width.

The block diagram below illustrates how to choose the correct motor (kit) for a specific bottom bracket:

Required parts for different bottom brackets

Here’s how it works in practice:

1. Bottom brackets with widths from 68 mm to 83 mm use the same 180 mm ISIS axle and left-side mounting part. Any excess space is adjusted with spacers. If your bike has a 68 mm BB shell, you’ll use the standard Photon kit and add 15 mm worth of spacers during installation. The kit includes 3 mm, 5 mm, and 7 mm spacers. A 73 mm BB requires 10 mm in spacers, while an 83 mm BB needs no spacers at all. The only downside to this is the increased Q-factor for shells narrower than 83 mm. The Q-factor in this setup is 200 mm.
2. BB92 press-fit brackets require a longer 200 mm axle, resulting in a 220 mm Q-factor. You’ll also need spacers here, as the 200 mm axle is designed for 100 mm BBs, while BB92 brackets are typically 92 mm wide. A longer left-side mounting piece is also necessary.
3. 100 mm BBs (fatbikes) use the same 200 mm axle—no spacers required.
4. 120 mm BBs (fatbikes) require a 220 mm axle, giving a Q-factor of 240 mm. You’ll also need a longer left-side mounting piece and a specially designed A-frame bracket with offset to reach the motor. All other setups use a flat A-frame bracket.

About the chainrings available for Photon kits

CYC Motor Photon kits come with several chainring options. Available sizes (number of teeth):

• 34T – extra cost
• 38T – standard
• 42T – standard
• 50T – extra cost

Obviously, different chainring sizes mean different diameters, which must be considered for frame compatibility. Larger chainrings may conflict with the rear triangle (chainstay). The chainring diameters are as follows: 148 mm, 160 mm, 176 mm, and 228 mm. There’s also a chainring guard, slightly larger in diameter, but since it’s spaced outward, it usually doesn’t cause clearance issues. In other words, if the chainring fits, the guard likely will too.

Why use different chainring sizes? For mountain bikes, where torque and cadence at lower speeds matter most—or for setups with limited cassette range—smaller chainrings (34T or 38T) are ideal. For gravel or trekking bikes, where speed matters more, 38T or 42T are solid choices. The 50T chainring was created for road bikes and fast gravel setups where high pedaling speed on flat terrain is the goal rather than climbing.

The weights of individual chainrings and other CYC Motor components can be found here: click here.

It’s worth noting that Photon chainrings are made of multiple bolted parts, called a “chainring assembly” by the manufacturer, which includes:

• adapter
• main (narrow-wide) chainring
• chainring guard

This matters because if the chainring wears out, you only need to replace that part, not the entire assembly—making it a cost-effective solution. Although disassembly requires the correct tools, chainring replacement isn’t a frequent need. We offer this service, including by mail.

Transferring an electric motor between bikes – an example

With the above knowledge, it’s easy to determine which extra parts are needed to move the motor between bikes. For example, we mounted our motor on a gravel bike with a 68 mm BB shell, and it also fit perfectly on an MTB with an 83 mm BB shell—no extra parts required. Now we’re moving it from the 83 mm MTB to a 120 mm fatbike. That means we need a longer axle, a longer left-side BB mounting piece, and a different A-frame bracket. The total cost of these parts is about 500 PLN. That’s a small price to pay for being able to enjoy winter riding in deep snow with a fatbike. For more on this fatbike build, check out this article – click here.

Here’s a visual story of how we transferred the electric motor from one bike to another—removing it from the full-suspension and installing it on the fatbike. An experienced user can complete the whole process in about two hours.

Step one – removing the motor from the full-suspension bike

Step two – installing the motor in the fatbike